ONCache: A Cache-Based Low-Overhead Container Overlay Network#
NSDI '25 digest Program Core pick 28–30 April 2025
- Authors / tier: Shengkai Lin, Shizhen Zhao, Peirui Cao, Xinchi Han (Shanghai Jiao Tong University); Quan Tian, Wenfeng Liu, Qi Wu, Donghai Han (Broadcom); Xinbing Wang (SJTU). Core.
- Why: Overlay networks (VXLAN/Geneve CNIs) are the default in Kubernetes but impose a per-packet tax versus bare metal. This is the exact tradeoff a cloud-native networking PM lives with, and the paper quantifies where the kernel datapath actually spends its time.
- What: The authors profile the overlay datapath segment by segment, observe that most of the extra overhead recomputes the same results across packets of a flow, and cache those invariant results. The result reaches near-bare-metal throughput while keeping overlay flexibility and compatibility.
- How: Three caches (egress, ingress, filter) hold the invariant per-flow results; implemented as four eBPF programs plus three eBPF maps and a small userspace component, in roughly 524 lines of eBPF C — far less than prior approaches like Slim or Falcon. Reported gains: ~12% TCP throughput and ~36% transaction-rate improvement (20%/34% for UDP), with reduced soft-interrupt CPU.
- Where applicable: Broadly applicable to overlay CNIs; the prototype is shipped as an Antrea plugin (Broadcom is a co-author), so the cleanest integration path is Antrea/OVS-based fabrics. The technique itself is CNI-agnostic.